System and method for discovering user equipment (UE) over side link in device to device (D2D) communication

ABSTRACT

The various embodiments of the present invention disclose a system and method for discovering User Equipment&#39;s over side link in device to device (D2D) communication. The present invention discloses new approaches for discovery and communication scheduling enabling optimum system performance with DRX alignment and meeting varied QoS targets. The present invention further addresses congestion handling during system overload situations. Further, the present invention discloses quality of service (QoS) scheduling methods that consider DRX function achieve substantial gains over existing methods.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Indian Provisional PatentApplication Serial No. 201641025050 filed on Jul. 21, 2016, in theIndian Intellectual Property Office, and to Indian Complete PatentApplication Serial No. 201641025050 filed on Jul. 3, 2017 in the IndianIntellectual Property Office, the entire disclosure of each of which isincorporated herein by reference.

1. TECHNICAL FIELD

The present invention generally relates to wireless communication andmore particularly, to a system and method for discovering user equipment(UE) over side link relay in device to device (D2D) communication.

2. DISCUSSION OF THE RELATED ART

Long term evolution (LTE) side-link (Device to device communication,D2D), also called as ProSe (Proximity Service) Relay, is being studiedand developed in 3GPP standard workgroups at present. It is aimed atequipping LTE to cater to critical communication services like publicsafety services like MC-PTT (Mission Critical Push to Talk) or GSCE(Group communication System Enablers) services as well as infotainmentbroadcast services like MBMS (Multimedia Broadcast Multicast services)providing audio/video streaming or text/data based services. It isdirected to extend the coverage area e.g. serving UEs (User Equipment)that are located outside of network coverage, also called Remote UEs(These UEs may still be in coverage of networks other than ProSenetworks being discussed). In general, these remote UEs are connected tothe ProSe networks through another UE called Relay UE which is incoverage of ProSe network. Thereby, Relay UE provides an indirect linkto the Remote UEs to the network. Relay UE may be connected to thenetwork by at least one of the multitude of the air interface techniqueslike cellular LTE, Multicast-broadcast single-frequency network (MBSFN),wireless local area network (WLAN), etc. whereas, it communicates withthe Remote UEs with side-link communication (i.e. D2D link).

Establishment and maintenance of side-link communication involves manyprocedures. FIG. 1 is a schematic flow diagram illustrating Type-1Discovery mechanism for ProSe Relay, according to an existing art.According to the FIG. 1, first of all Remote UE needs to discover theRelay UE which can provide its service of interest. For this purpose, aremote UE can monitor the periodical announcements being made by theRelay UE and accordingly get associated with the Relay UE based on thesufficient signal conditions of the link.

FIG. 2 is a schematic flow diagram illustrating Type-2 DiscoveryMechanism, according to an existing art. According to the FIG. 2, aRemote UE sends a solicitation messages and based on response of theRelay UE gets associated with it after determining signal conditions areadequate.

Once getting associated a Layer-2 Link is established between the Remoteand Relay UE for one-to-one ProSe Direct Communication, wherein datatransmissions and reception between Remote UE and Relay UE takes place.Also, at the same time Remote UE keeps monitoring the signal conditionsof the link to ensure connectivity. In case of deterioration of thelink, it may start searching for a different Relay; this process iscalled Relay reselection.

FIG. 3 is a schematic flow diagram illustrating disconnect procedure,according to an existing art. According to the FIG. 3, after thenecessary communications over the sidelink channel are completed theRemote UE or Relay UE can release the Layer-2 Link by sending theDisconnect Request Sidelink message.

Many potential issues are noticed with the existing system andprocedures for LTE Side-link Relay communication. One of the problemsbeing addressed in this invention is how to optimize the energyefficiency by reducing the power consumption at the prose Network-to-UERelay (also called Relay) and Remote UEs. The power consumption dependson multiple factors—number of remote UEs being served, DRX cycle of therelay and remote UE and the delay tolerance of the services. The RelayUE's power consumption would increase as the number of remote UEs beingserved increases, the DRX cycle of the remote UEs hugely differs fromeach other and from the relay UE and if the delay tolerance of theservice is very less, which in turn reduces the energy efficiency of therelay UE. Other aspects and issues involved for LTE side-link Relaycommunication is about how to aggregate service data pertaining to oneor more Remote UEs and how to schedule transmissions with meeting theneeded Quality of Service (QoS) for each of the service for each of theRemote UEs involved in Relay communication.

Further, discovery procedure for Relay Networks have been objective indefining procedures for finding Relay UE, but Remote UEdiscovery/identification is not properly addressed.

Currently, no procedure is present in 3GPP specs to handle congestion onRelay UE, which may get overloaded when catering multiple Remote UEs.Further, service Continuity aspects for remote UEs are not yet addressedin 3GPP specs.

Further, currently, the LTE side-link Relay communication is the 3GPPstandard. It does not address the aspects and issues explainedaforementioned and resultantly leads to sub-optimum performance of theRelay system including both Relay UE and Remote UEs.

Thus there is a need for a system and method for device to device (D2D)communication with the side-link relay to overcome the higher powerconsumption and optimize energy efficiency. Further, there is a need fora system and method for enhancing Remote UE identification and discoveryprocedures while specifying messages and their contents required forsuch an enhancement. Further, there is a need for a system and methodwith Congestion Handling Scheme for Relay systems.

Further, there is a need for a system and methods that uses specificprocedures catering to the herein above mentioned issues using retry,redirection, load balancing, and the like. Further, there is need forsolutions aiming at maintaining a seamless Relay services.

The above mentioned shortcomings, disadvantages and problems areaddressed herein and which will be understood by reading and studyingthe following specification.

SUMMARY

The various embodiments of the present invention disclose a system andmethod for discovering user equipment (UE) over side link relay indevice to device (D2D) communication. According to an embodiment of thepresent invention, a method for discovering User Equipment (UE) overside link in device to device (D2D) communication, the method comprisessteps of receiving, by a relay User Equipment (UE), a solicitationmessage from a remote User Equipment (UE), wherein the solicitationmessage comprises of one or more combination of information including anUE identity, QoS Requirements, DRX configuration signals, currenttransmission power (Tx Pwr), and transmitting, by the relay UE, a devicediscovery response along with a support status message to the remote UEbased on the UE Id in the solicitation message.

In an embodiment of the present invention, the relay UE transmits thedevice discovery response based on at least one of, but not limited to,QoS/latency bounds supportable, checking if Energy consumption is withinthreshold for Relay UE if admitting the soliciting remote UE with itsTx_Pwr, number of currently serving remote UEs is under limit, remote UEdevice type, bandwidth, and the like, without departing from the scopeof the invention.

According to an embodiment of the present invention, a method fordiscovering User Equipment (UE) over side link in device to device (D2D)communication, the method comprises steps of receiving, by a relay UserEquipment (UE), a solicitation message from a remote User Equipment(UE), wherein the solicitation message comprises of an UE identity, QoSRequirement i.e. packet delay budget/latency bound, DRX configurationsignals, current transmission power (Tx Pwr), determining, by the relayUE, a relay load status as overloaded or congested if the Remote UE isin coverage area and a Type 2 discovery method is used, and respondingin Solicitation response message with an overload indication, if therelay load status is overloaded.

In an embodiment of the present invention, in a Type 2 Discovery, theRelay UE responds in Solicitation response message with an overloadindication and/or back-off indication or back-off duration value. In anembodiment of the present invention, if the QoS requested by the remoteUE is not supported by the Relay UE, the Relay UE indicates the supportstatus as negative.

According to another embodiment of the present invention, a method fordiscovering User Equipment (UE) over side link in device to device (D2D)communication, the method comprises steps of checking, by a relay UE,the QoS (latency bounds) information in a solicitation message receivedfrom one or more remote UEs, scheduling one or more service and remoteUE transmissions in priority order based on a latency requirements ofthe one or more remote UEs, preparing RX scheduling patterns based onthe latency requirements, and assigning the RX scheduling patterns tothe one or more remote UEs with aligning DRXs between relay and one ormore remote UE(s).

According to another embodiment of the present invention, a method forenabling side link relay discovery in device to device (D2D)communication, the method comprises steps of receiving, by one or morerelay User Equipment's (UE), a solicitation message transmitted by aremote User Equipment (UE), and transmitting, by the one or more relayUEs which are currently overloaded, a solicitation response message inType 2 discovery, wherein the solicitation response message comprises ofoverload status indicating whether the relay UE is overloaded.

In an embodiment of the present invention, the method further comprisesof receiving, by one or more remote User Equipment's (UE), anannouncement message transmitted by a relay User Equipment (UE) in type1 discovery, wherein the announcement message comprises of overloadstatus indicating whether the relay UE is overloaded, ignoring, by oneor more remote UEs, congestion status if the remote UE is alreadyconnected, obtaining, by the one or more remote UEs, PC5 measurements tocheck if relay reselection criteria meets, abandoning, by one or moreremote UEs, selection or reselection of the relay UE if they areinterested to connect or trying to connect, and abandoning, by one ormore Remote UEs, PC5 measurements for the Relay UE to check for relayreselection criteria.

In another embodiment of the present invention, the method furthercomprises steps of transmitting, by the one or more Relay UEs, anoverload indicator during a Master Information Block (MIB) broadcastindicating whether the UE relay is overloaded or not, and avoiding bythe one or more out of coverage remote UEs, sending of the SolicitationRequest message to the one or more relay UEs which are overloaded.

In another embodiment of the present invention, the method furthercomprises of backing off, by the one or more remote UEs, from sendingthe solicitation request message on receiving the overload indicatorfrom the relay UEs, wherein the back-off duration is pre-provisioned tobe selected from a predefined range.

According to an embodiment of the present invention, a method forenabling side link relay discovery in device to device (D2D)communication, the method comprises steps of receiving, by a relay UserEquipment (UE), a DRX configuration request from a remote User Equipment(UE) over a PC-5 link, determining, by the relay UE, an optimal DRXconfiguration for the remote UE, and sending, by the relay UE, the DRXconfiguration to the remote UE over the PC5 link and ensures no data istransmitted to the remote UE during the DRX period.

In an embodiment of the present invention, the DRX configuration requestcomprises of, but not limited to, a state indicator, and DRX parameters,without departing from the scope of the invention. In another embodimentof the present invention, the remote UE applies both Unicast andside-link DRX configuration to determine an active DRX period.

In another embodiment of the present invention, the Relay UE determinesoptimal DRX configuration based on at least one of, but not limited to,alignment for DRX configuration used by the Remote UE and the Relay UE,services and their corresponding scheduling information, providing sameDRX config as its own or a sub-set of it based on service needs,QoS/latency bounds of the service, the received configurations from theeNB, selected configuration from a pool of configurations, and the like,without departing from the scope of the invention.

According to another embodiment of the present invention, a method forenabling side link relay discovery in device to device (D2D)communication, the method comprises steps of receiving, by a relay UserEquipment (UE), a data set from a network, performing, by the relay UE,data aggregation of transmission data, performing, by the relay UE, adata transmission to a remote UE according to the configured DRX, andreceiving, by the relay UE, data transmitted by the remote UE accordingto the configured DRX.

In an embodiment of the present invention, the Relay UE utilizes the QoS(latency bounds) information received from the Remote UE in deciding howmuch aggregation and transmission delay can be incurred at Relay UE sideand scheduling transmissions for the remote UEs.

According to another embodiment of the present invention, method ofdisconnecting

Comprises steps of sending, by a relay UE, a disconnection request to aremote UE along with a redirection information for switching of remoteUE to another Relay User Equipment (UE), and receiving, by the relay UE,a disconnect response from the remote UE.

In an embodiment of the present invention, the relay UE acquires theredirection information that includes redirection information based onSIB19 which out of coverage Remote UEs can utilize.

According to another embodiment of the present invention, a Relay UserEquipment (UE) for side-link communication comprising a Remote-RelayController (RR controller) adapted for providing RX patterns assignmentto remote UE(s) with aligning DRXs between relay and remote UE(s),Traffic identification and differentiation, Service Data aggregation forremote UE(s), and QoS based scheduling transmission. Further, the relayUE comprises of a router module adapted to connect a cellular link to aside-link with a L3 forwarding based approach, a side-link stack adaptedfor enabling communication with one or more remote User Equipment's(UEs) connected to the relay UE, and an interface technique forconnecting the relay UE to the cellular network, where the networkinterface comprises at least one of, but not limited to, a cellularLong-Term Evolution (LTE) network, Multicast-broadcast single-frequencynetwork (MBSFN), wireless local area network (WLAN), and the like,without departing from the scope of the invention.

The foregoing has outlined, in general, the various aspects of theinvention and is to serve as an aid to better understanding the morecomplete detailed description which is to follow. In reference to such,there is to be a clear understanding that the present invention is notlimited to the method or application of use described and illustratedherein. It is intended that any other advantages and objects of thepresent invention that become apparent or obvious from the detaileddescription or illustrations contained herein are within the scope ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The other objects, features and advantages will occur to those skilledin the art from the following description of the preferred embodimentand the accompanying drawings in which:

FIG. 1 is a schematic flow diagram illustrating Type-1 Discoverymechanism for ProSe Relay, according to an existing art.

FIG. 2 is a schematic flow diagram illustrating Type-2 DiscoveryMechanism, according to an existing art.

FIG. 3 is a schematic flow diagram illustrating disconnect procedure,according to an existing art.

FIG. 4 is a schematic block diagram illustrating architecture forside-link Relay, according to an embodiment of the present invention.

FIG. 5 is a schematic flow diagram illustrating a relay discoveryapproach, according to an embodiment of the present invention.

FIG. 6 is a schematic flow diagram illustrating a discovery approach foroverload case, according to an embodiment of the present invention.

FIG. 7 is a schematic diagram illustrating congestion handling,according to an embodiment of the present invention.

FIG. 8 is a schematic flow diagram illustrating redirection, accordingto an embodiment of the present invention.

FIG. 9 is a schematic diagram illustrating approach for redirection,according to an embodiment of the present invention.

FIG. 10 is a schematic flow diagram illustrating type-2 approach fordiscovery, according to an embodiment of the present invention.

FIG. 11 is a schematic diagram illustrating type-1 discovery approachfor V2X scenario, according to an embodiment of the present invention.

FIG. 12 is a schematic flow diagram illustrating approach for DRX,according to an embodiment of the present invention.

FIG. 13 is a schematic flow diagram illustrating approach for DRX anddata aggregation, according to an embodiment of the present invention.

Although specific features of the present invention are shown in somedrawings and not in others. This is done for convenience only as eachfeature may be combined with any or all of the other features inaccordance with the present invention.

DETAILED DESCRIPTION

The various embodiments of the present invention disclose a system andmethod for discovering user equipment (UE) over side link in device todevice (D2D) communication. In the following detailed description of theembodiments of the invention, reference is made to the accompanyingdrawings that form a part hereof, and in which are shown by way ofillustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and that changesmay be made without departing from the scope of the present invention.The following detailed description is, therefore, not to be taken in alimiting sense, and the scope of the present invention is defined onlyby the appended claims.

The specification may refer to “an”, “one” or “some” embodiment(s) inseveral locations. This does not necessarily imply that each suchreference is to the same embodiment(s), or that the feature only appliesto a single embodiment. Single features of different embodiments mayalso be combined to provide other embodiments.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless expressly stated otherwise. Itwill be further understood that the terms “includes”, “comprises”,“including” and/or “comprising” when used in this specification, specifythe presence of stated features, integers, steps, operations, elementsand/or components, but do not preclude the presence or addition of oneor more other features integers, steps, operations, elements,components, and/or groups thereof. As used herein, the term “and/or”includes any and all combinations and arrangements of one or more of theassociated listed items.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure pertains. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

The present invention provides a system and method for discovering UserEquipment (UE) over side link in device to device (D2D) communication.The UE can be any of the electronic communication devices such as, butnot limited to, mobile phone, laptop, tablet, PDA, smart watch, smartglasses, and the like. The person having ordinarily skilled in the artcan understand that the described embodiments use cases are for betterunderstanding and illustration of the present invention, but not limitto scope of the present invention.

According to an embodiment of the present invention, a method fordiscovering User Equipment (UE) over side link in device to device (D2D)communication, the method comprises of receiving, by a relay UserEquipment (UE), a solicitation message from a remote User Equipment(UE), wherein the solicitation message comprises of one or morecombination of information including an UE identity, quality of service(QoS) Requirements, DRX configuration signals, current transmissionpower (Tx Pwr). During D2D communication, the communication can beestablished between the relay UE and the remote UE. During D2Dcommunication, the remote UE transmits the solicitation message to therelay UE, wherein the solicitation message comprises of information suchas, but not limited to, UE identity (Id), quality of service (QoS)Requirements, DRX configuration signals, current transmission power (TxPwr), and the like. The relay UE receives the solicitation message alongwith the information needed for D2D communication.

Further, the method comprises of the relay UE transmitting a devicediscovery response along with a support status message to the remote UEbased on the UE Id in the solicitation message. Based on the receivedsolicitation message, the relay UE identifies whether D2D communicationcan be established with the remote UE or not. And based on the receivedinformation and identified values, the relay UE transmits the responseto the remote UE along with the support status message indicatingwhether the communication can be established or not.

In an embodiment of the present invention, the relay UE transmits thedevice discovery response based on at least one of, but not limited to,QoS/latency bounds supportable or not, checking if Energy consumption iswithin threshold for Relay UE if admitting the soliciting remote UE withits Tx_Pwr, number of currently serving remote UEs is under limit,remote UE device type, Bandwidth, and the like, without departing fromthe scope of the invention.

According to another embodiment of the present invention, a method fordiscovering User Equipment (UE) over side link in device to device (D2D)communication, the method comprises steps of receiving, by a relay UserEquipment (UE), a solicitation message from a remote User Equipment(UE), wherein the solicitation message comprises of an UE identity (Id),QoS Requirement, DRX configuration signals, current transmission power(Tx Pwr), and the like, wherein the QoS requirement can include, but notlimited to, packet delay budget/latency bound, without departing fromthe scope of the invention.

Further, the method comprises of responding in Solicitation responsemessage with an overload indication, if the relay load status isoverloaded. If the relay UE identifies that the relay overload status ofthe remote UE is overloaded, then the relay UE transmits thesolicitation response message to the remote UE with an indication ofoverload in the message.

In an embodiment of the present invention, in a Type 2 Discovery, theRelay UE responds in Solicitation response message with an overloadindication and/or back-off indication or back-off duration value.

In an embodiment of the present invention, if the QoS requested by theremote UE is not supported by the Relay UE, then the Relay UE indicatesthe support status as negative.

According to an embodiment of the present invention, a method fordiscovering User Equipment (UE) over side link in device to device (D2D)communication, the method comprises steps of a relay UE checking QoSinformation in a solicitation message received from one or more remoteUEs, wherein the QoS information comprises of latency bounds. The remoteUE transmits solicitation message to the relay UE along with QoSinformation that comprises of latency bounds. The relay UE receives thesolicitation message and checks for the QoS information.

Further, the method comprises of scheduling one or more service andremote UE transmissions in priority order based on a latencyrequirements of the one or more remote UEs. Based on the latencyrequirements of the one or more remote UEs, one or more services andremote UE transmissions can be scheduled.

Further, the method comprises of relay UE preparing receiving (RX)scheduling patterns based on the latency requirements. Further, themethod comprises of assigning the RX scheduling patterns to the one ormore remote UEs with aligning DRXs between relay and one or more remoteUE(s).

According to another embodiment of the present invention, a method forenabling side link relay discovery in device to device (D2D)communication, the method comprises steps of receiving, by one or morerelay User Equipment's (UE), a solicitation message transmitted by anin-coverage remote User Equipment (UE). In the present embodiment, theremote UE is in the coverage region of one or more relay UEs, andtransmits solicitation message to the one or more relay UEs. The relayUEs receives the solicitation message transmitted by the remote UE.

Further, the method comprises of one or more relay UEs, which arecurrently overloaded, transmits a solicitation response message in Type2 discovery. Further, the method comprises of the one or more relay UEswhich are currently overloaded transmit an announcement message alongwith an overload indication in Type 1 discovery.

In an embodiment of the present invention, the method further comprisessteps of transmitting, by the one or more Relay UEs, an overloadindicator during a Master Information Block (MIB) broadcast indicatingwhether the UE relay is overloaded or not. During transmitting thesolicitation response, the one or more relay UEs transmit overloadindicator during the master information block (MIB) broadcast thatindicates whether the relay UE is overloaded or not. Further, the methodcomprises of the one or more out of coverage remote UEs avoiding sendingof the Solicitation Request message to the one or more relay UEs whichare overloaded.

In another embodiment of the present invention, the method furthercomprises of backing off, by the one or more remote UEs, from sendingthe solicitation request message on receiving the overload indicatorfrom the relay UEs, wherein the back-off duration is pre-provisioned tobe selected from a predefined range.

According to another embodiment of the present invention, a method forenabling side link relay discovery in device to device (D2D)communication, the method comprises steps of receiving, by a relay UserEquipment (UE), a DRX configuration request from a remote User Equipment(UE) over a PC-5 link. The remote UE transmits the DRX configurationrequest to the relay UE over the PC-5 link. Further, the methodcomprises of based on the received DRX configuration request, the relayUE determines an optimal DRX configuration for the remote UE. Further,the method comprises of the relay UE sending the DRX configuration tothe remote UE over the PC5 link and ensures no data is transmitted tothe remote UE during the DRX period.

In an embodiment of the present invention, the DRX configuration requestcomprises of, but not limited to, a state indicator, DRX parameters, andthe like, without departing from the scope of the invention.

In another embodiment of the present invention, the remote UE appliesboth Unicast and side-link DRX configuration to determine an active DRXperiod. In another embodiment of the present invention, the Relay UEdetermines optimal DRX configuration based on one of, but not limitedto, alignment for DRX configuration used by the Remote UE and the RelayUE, based on services and their corresponding scheduling information,providing same DRX config as its own or a sub-set of it based on serviceneeds, QoS/latency bounds, and the like, without departing from thescope of the invention.

According to another embodiment of the present invention, a method forenabling side link relay discovery in device to device (D2D)communication, the method comprises steps of receiving, by a relay UserEquipment (UE), a data set from a network. The network transmits thedataset to the relay UE. Further, the method comprises of the relay UEperforming data aggregation which is in accordance to the acceptabletransmission delay for the concerned data. Further, the method comprisesof performing, by the relay UE, a data transmission to a remote UEaccording to the configured DRX. Further, the method comprises ofreceiving, by the relay UE, data transmitted by the remote UE accordingto the configured DRX.

In an embodiment of the present invention, the Relay UE utilizes the QoS(latency bounds) information received from the Remote UE in deciding howmuch aggregation and transmission delay can be incurred at Relay UE sideand scheduling transmissions for the remote UEs.

According to another embodiment of the present invention, method ofdisconnecting comprises steps of sending, by a relay UE, a disconnectionrequest to a remote UE along with redirection information for switchingof remote UE to another Relay User Equipment (UE). Further, the methodcomprises of receiving, by the relay UE, a disconnect response from theremote UE.

In an embodiment of the present invention, the relay UE acquires theredirection information based on at least one of, but not limited to,redirection information based on SIB19 which Out of Coverage Remote UEscan utilize, and the like, without departing from the scope of theinvention. Here in, Redirection information in SIB19 provides list ofside-link EARFCNs or frequencies which is used in the vicinity. Further,redirection information could be for switching form sidelink relay toLTE unicast connection in the case there is no proper or none otherRelay UE is present in vicinity or not able to support the requiredservice.

According to another embodiment of the present invention, a relay UserEquipment (UE) for side-link communication, the relay UE comprises aRemote-Relay Controller (RR controller), a router module, a side-linkstack, and an interface. According to the present invention, theRemote-Relay Controller (RR controller) is adapted for providing RXpatterns assignment to remote UE(s) with aligning DRXs between relay andremote UE(s), traffic identification and differentiation, service dataaggregation for remote UE(s), and QoS based scheduling transmission.

Further, the router module is adapted to connect a cellular link to aside-link with a L3 forwarding based approach. Further, the side-linkstack is adapted for enabling communication with one or more remote UserEquipment's (UEs) connected to the relay UE. Further, the interfacetechnique is adapted for connecting the relay UE to the cellularnetwork, wherein the network interface comprises at least one of acellular Long-Term Evolution (LTE) network, Multicast-broadcastsingle-frequency network (MBSFN), wireless local area network (WLAN),and the like, without departing from the scope of the invention.

FIG. 4 is a schematic flow diagram 400 illustrating a relay discoveryapproach, according to an embodiment of the present invention. Accordingto the relay discovery approach as described in FIG. 4, the discoveryapproach for D2D communication is between a remote UE 402 and a relay UE404. According to the embodiment, at step 406, the remote UE 402 sends asolicitation message in order to discover a Relay UE 404 to meet itsdesired service and includes one or combinations of information in themessage including, but not limited to, UE identity, QoS Requirement i.e.packet delay budget/latency bound of the service, DRX configuration andstate, such as, whether the remote UE is out of coverage or in idle DRXor connected DRX with some external network and the configuration forthe DRX, its current transmission power with which it is transmittingthe message to the Relay UE, and the like.

Remote UE 402 identification during discovery is performed with UE Id inSolicitation Request. Signaling type of device (Normal/wearable/V2X),type of interface, bandwidth (BW), uplink (UL)/downlink (DL) directionssupport and the like are encoded in prefix portion of UE Id. Remainderportion carries device identification. Based on identification, Relay UE404 decides on support status and suitable configurations. Further UE Idis utilized during communication phase also wherein with the aid of UEId network can distinguish the traffic packets coming from differentRemote UEs and also from the traffic packets originated from the RelayUE. For this purpose the traffic packet carries the UE Id in the headerof the packet. This also facilitates mapping of the packet acrossdifferent bearers and links based on QoS requirements. Also in thereverse direction wherein packets are being received from network atRelay UE, they can be properly destined to the relay UE itself andtowards different Remote UEs with suitable QoS priority for transmissionbased on the identification of UE_Id. In some cases, where same trafficis consumed by both Relay UE and one or more Remote UE(s), packets arecopied and passed to both destinations instead of double decoding.

Further the UE_ID can be used or mapped to another suitableidentification for paging purpose by the network to send a pageindication to the Remote UE e.g. arrival of DL data or call.

QoS requirement is indicated in terms of latency bounds and/or QoS classidentifier. DRX configuration (config) signals the idle/conn mode DRXand DRX parameters like DRX cycle etc. Relay device provides a DRXfilter to remote device in order to conserve power and schedule itstransmission. Tx Pwr is the transmission power used by the remote UE 402for the message. Relay UE 404 determines the energy requirements basedon this to support/add this remote device.

At step 408, the relay UE responds with support status based on such as,but not limited to, QoS/latency bounds supportable, Energy consumptionwithin threshold for Relay UE if admitting the soliciting Remote UE withits Tx_Pwr, Number of existing being served Remote UEs under limit,Remote UE device type, BW, capability supportable and the like, withoutdeparting from the scope of the invention.

Since remote UE 402 is hidden to network, ensuring End-to-End QoS forthe different services in a relay system is a challenge as can at mostsupport QoS for the link between the network and the relay. Theinvention here proposes to ensure End-to-End QoS for service i.e.between the network and the remote UE 402 via the Relay UE 404. Approachincludes both network assisted in which relay UE makes network awareabout the specific need for QoS of a given service and networkindependent in which relay UE itself takes care to ensure desired QoS isachieved by taking scheduling and transmission operations accordingly tomeet QoS as described ahead. It is possible to employ a combinedapproach in which both steps including that network is made aware andRelay UE 404 also undertakes steps and operations to ensure desired QoSis met for concerned services. These services can include differenttraffic types that include VOIP, streaming services, instant messaging,browsing, MTC traffic and download applications.

Further, the relay UE 404 utilizes the QoS (latency bounds) informationreceived from Remote UE 402 in deciding how much aggregation (storing)and transmission delay can be incurred at Relay side and schedulingtransmissions for Remote UEs 402. Different Services and Remote UEs 402transmissions are scheduled in priority order in terms of their latencyrequirements. Accordingly DRX filters (RX scheduling patterns) areprepared and signaled to Remote UEs 402. Based on TrafficDifferentiation Relay UE 404 employs different HARQ/RLC Profiling basedto meet latency and reliability needs e.g. AM/UM mode, retransmissionsetc. Additionally for persistent natured services, SPS/periodicscheduling is carried out. Alternatively, DRX configuration can beobtained by Relay UE from the network, after it informs network on theDRX requirements for the remote UE. Then Relay Ue provides the DRXconfiguration to the remote UE. With this approach network is also madeaware about the DRx requirements on the sidelink and can help in theoverall link operation from network through Relay UE to Remote UEefficiently. This approach also depends on the connected and idle modeof the UE. Also, the DRX configuration indication from network can beexplicitly provided or indicated through an index to the preconfiguredlist of configurations or chosen by the Relay UE from the pool of DRxconfigurations.

FIG. 5 is a schematic flow diagram 500 illustrating a discovery approachfor overload case, according to an embodiment of the present invention.According to the FIG. 5, the diagram comprises of a remote UE 502 asdiscoverer, two relay UEs, relay UE1 504 and relay UE2 506 asdiscoveries (devices which are being discovered). At step 508, both theRelay UEs 504 and 506 in case of type-2 Discovery method, receives asolicitation request message from the Remote UE 502, and determines theRelay load status whether it is overloaded or congested i.e., alreadyserving maximum possible Remote UEs and/or services. In the presentcase, relay UE1 504 is not overloaded and relay UE2 506 is overloaded.Thus, at step 510, the relay UE2 506 responds through the discoveryresponse message with an overload indication and/or back-off indicationor duration value for back-off. Further, at step 512, the relay UE1 504responds through the discovery response message with not overloadedindication. In an embodiment of the present invention, in case of Type-1Discovery method, the Relay UE1 504 transmits “Announcement” withoverload indication. The Remote UEs, that are already connected toRelay, will ignore the Overload indication received in Announcement andperform PC5 measurements. But the Remote UEs that are not connected toRelay UE will process the Overload indication and act accordingly, andthus would not connect or reselect to these Relay UEs that areoverloaded. Further, PC5 measurements are also abandoned for these RelayUEs.

FIG. 6 is a schematic diagram 600 illustrating congestion handling,according to an embodiment of the present invention. According to theFIG. 6, in case of Out of Coverage Remote UE scenario, the Relay UEsadvertise their Overload status during the MIB broadcast. An Out ofCoverage Remote UE would first need to synchronize with Relay UEs beforeinitiating the Discovery procedure, thus by including the OverloadStatus in MIB-SL the Relay UEs can avoid unnecessary SolicitationRequest from Remote UEs thereby avoiding flooding at the Relay side andwastage of limited Discovery resources. Flooding is quite critical dueto possibility of large number of remote UEs in the system causingredundant transmissions. Remote UEs, therefore, also avoid synchronizingto those relays that are overloaded.

An Out of Coverage Remote UE after decoding the MIB-SL of Relays wouldknow if they are overloaded through the “Overload Indicator” and avoidsending Solicitation Request. Remote UEs can apply back-off andreattempt connecting to an Overloaded Relay UE; the back-off can eitherbe explicitly broadcast by the Relay UE or pre-configured in the RemoteUEs e.g. SIM can be preconfigured.

FIG. 7 is a schematic flow diagram 700 illustrating redirection,according to an embodiment of the present invention. According to FIG.7, the flow diagram 700 comprises of a relay UE 702 and a remote UE 704.if the Relay UE 702 needs to provide service for a higher priorityRemote UE 704 or if the Relay UE 702 is being shut down or if therequested QoS of the remote UE 704 is not supportable by Relay UE 702,then the Remote UE 704 is redirected to search a different Relay UE 702to get continued service or obtain its desired QoS service. At step 706,the Relay UE 702 can provide the Redirection Information in theDisconnect Request message. Upon receiving the message, at step 708, theremote UE 704 can transmit the disconnect response message to the relayUE 702 indicating if it is ready to disconnect from the relay UE 702 andready to connect with another relay UE.

FIG. 8 is a schematic diagram 800 illustrating approach for redirection,according to an embodiment of the present invention. According to FIG.8, the Relay UE can acquire the Redirection information from the eNB.The eNB can broadcast the frequencies that are being used for sidelinkin the vicinity via SIB 19. And the Relay UE can use the samefrequencies received in SIB 19 in the Redirection information for theRemote UEs. Remote UEs which are not in coverage of network, therefore,can also obtain the information.

Furthermore, in an embodiment of the present invention, the systemcaptures the aspect of differentiating different types of UE operatingin side-link. In Rel.14 system, there would be different types of UEsand nodes that would be discovering for other UEs over the side-link,these include mobile devices, vehicles and road side units. As all thesedevices communicate using side-link resources (V2X scenario) it becomesnecessary to differentiate among them. For example a normal mobiledevice would be interested to act as a Remote UE for Public Safety andnot interested in interacting with vehicles or road side units.

FIG. 9 is a schematic flow diagram 900 illustrating type-1 approach fordiscovery, according to an embodiment of the present invention.According to the FIG. 9, the flow diagram 900 comprises of two userequipment's (UE), UE1 902 and UE2 904. According to the FIG. 9, inType-1 Discovery, at step 906, the UE1 902 that is making theAnnouncement would send a solicitation request that includes UE type.All the other devices, including UE 904, receives the Announcement, andat step 908, would initiate communication in the form of solicitationresponse message, only if it is interested in communicating with thatparticular UE type.

FIG. 10 is a schematic flow diagram 1000 illustrating type-2 approachfor discovery, according to an embodiment of the present invention.According to the FIG. 10, the flow diagram 1000 comprises of three UEs,UE1 1002, UE2 1004, and UE3 1006. At step 1008, in Type-2 Discovery, theUE1 1002 being discoverer device will include its UE type in theSolicitation Request. All the other devices, UE2 1004 and UE3 1006,receiving the Request, would send a Solicitation Response, only if theyare interested in communicating with that UE type.

FIG. 11 is a schematic flow diagram 1100 illustrating approach for DRX,according to an embodiment of the present invention. According to theFIG. 11, the flow diagram 1100 comprises of a remote UE 1102, a relay UE1104, and eNode (eNB) 1106.

For data reception, a remote UE needs to be awake and monitor entire Rxoccasions which are a superset of all the relay Tx opportunities, eventhough data may not be scheduled always, causing poor DRX operation andheavy power consumption. At the same time, individual remote UEs may beunder different configurations for Connected/Idle DRX with their ownnetworks and have different QoS requirements for their services.

According to the FIG. 11, the Relay UE 1104, on the basis of latencybounds information and DRX configuration and state of Remote UE 1102,determines the DRX filter which is the subset of the RX occasions thatwill be utilized for Relay to Remote communication and indicates thisDRX filter to Remote UE 1102 in Discovery Response message. Whileselecting this subset, consideration is given to choose such thatselected subset is aligned with the DRX of remote UEs and/or Relay UE1104. With better alignment with existing DRX patterns, power saving isboosted for both Relay and Remote UEs.

During communication phase, at step 1108, the Remote UE 1102 transmitsits current state (Idle, Connected, Out Of Coverage or OOC) and unicastDRX configurations for connected state over the PC-5 link to the RelayUE 1104 and requests it to provide the Sidelink DRX configurations basedon the parameters shared with the Relay UE 1104 thus far.

At step 1110, the Relay UE 1104 determines optimal DRX configurationbased on multiple approaches—

1. Alignment of DRX configurations used in both Remote UE 1102 and RelayUE 1104,

2. By taking into account the QoS and latency requirements of the RemoteUE 1102,

3. Providing same DRX configurations as its own or a subset of it basedon service and scheduling needs.

Further, at step 1112, the relay UE 1104 sends the DRX configuration toremote UE 1102 over PC5 link and makes sure for no transmission duringDRX period. Remote UE 1102 applies both Unicast and side-link DRXconfiguration to determine active period in conn mode. Based on stateand service scheduling, DRX config/pattern can be dynamically updated.

FIG. 12 is a schematic flow diagram 1200 illustrating approach for DRXand data aggregation, according to an embodiment of the presentinvention. According to the FIG. 12, the flow diagram 1200 comprises ofa remote UE 1202, a relay UE 1204, and eNode (eNB) 1206. According tothe flow diagram 1200, the relay UE 1204 aggregates service data whichis received from main link (cellular, MBSFN etc) and stores temporarilyuntil TX opportunities determined as per DRX alignment and QoSrequirement is met and tries to maximize the power saving.

When transmission opportunities are met as per determination, the RelayUE 1204 undertakes burst mode of transmission to quickly send out thedata towards the Remote UEs 1202. The Relay UE 1202 schedulestransmission in priority order of service QoS for each of the remote UEs1202 connected to it. This ensures the required service latency orpacket delay budget is not overshoot for packets pertaining to thedefined QoS. In another embodiment, it is described that the Relay UEprovides the configuration for the TX/RX gaps information for side-linkcommunication to remote UE 1202 through PC-5 link (side-link) so thatthe Relay UE 1204 and Remote UEs 1202 are in sync for TX and RX andsaves power during non-transmission and no-reception periods (gaps).

Further, the Relay UE 1204 dynamically updates the configuration changesas applicable to Relay UE 1204 and Remote UE 1202 and iterative appliesthe scheduling algorithm as discussed to achieve best possibleperformance.

In another embodiment of the present invention, the Relay UE 1204 andRemote UE 1202 can be constituents of V2V (Vehicle to Vehicle) or V2X(Vehicle to Everything) communication system and services they carry maybe public safety messages and/or traffic related alerts and/orinfotainments services data etc.

In another embodiment of the present invention, the remote UE 1202 couldbe wearables and relay UE 1204 could be smartphones that formRelay-Remote communication system and can utilize LTE, D2D, WirelessLAN, Bluetooth, Machine Type Communication or Narrow Band communicationto interact and transfer data across.

In another embodiment of the present invention, the Relay UE 1204 can be5G devices and that aid to extend the 5G communication coverage toindoors environment wherein Remote devices located inside are notreachable with 5G communication. This is due to limitation of themillimeter waves to be used in 5G which are short range and suffersextreme high attenuation in propagating through certain buildingmaterials like bricks, concrete etc. and resultantly, renders 5Gcoverage to be limited to outdoors. The proposed Relay-Remote system canthus extend 5G communication to indoors and also extend its range ofcoverage.

FIG. 13 is a schematic block diagram 1300 illustrating architecture fora relay UE 1300 with side-link Relay, according to an embodiment of thepresent invention. According to the FIG. 13, the relay UE 1300 comprisesof a RR (Relay-Remote) Controller 1302, application and middleware 1304,a L3 router 1306, a sidelink stack 1308, a LTE stack 1310, and a MBSFNstack 1312. Further, the relay UE 1300 can be connected to one or moreremote UEs remote UE1 1314 a, remote UE2 1314 b, remote UE3 1314 c, anda cellular network 1316.

According to the present invention, the RR controller 1302 handlesadmission control through discovery process and employs communicationscheduling strategies. The RR controller 1302 determines the schedulingtransmission occasions towards remote UEs maximizing overall systemenergy efficiency, providing remote UEs operational DRX patterns fortheir sleep operation and meeting QoS requirements for pertinent publicsafety or broadcast services. Multiple stacks in the relay cater toreception capability through different cellular air interface techniqueslike sidelink stack 1308, LTE stack 1310, MBSFN stack 1312, and thelike. L3 Router module 1306 bridges the cellular link to side-link witha L3 forwarding based approach. Side-link communication serves to one ormore remote UE(s) connected with the relay.

Proposed functionalities of the RR controller 1302 are: a) RX patternsassignment to remote UE(s) with aligning DRXs between relay and remoteUE(s), b) Traffic identification and differentiation, c) Service Dataaggregation for remote UE(s), and d) QoS based scheduling transmission.RR controller 1302 employs common buffer for service data aggregationwith suitable indexing and identification of services while renderingdifferential treatment based on QoS requirements. This is applied inboth directions viz. downlink and uplink. Mapping is maintained betweenside-link services and cellular link bearers and also involves priorityhandling and sending data based on QoS needs e.g. delay sensitive datais provided at earliest for transmission.

In an embodiment of the present invention, a state machine is proposedfor side-link Relay. State machine for Relay operation includesfollowing states: Sleep state—where in Relay UE 1300 remains in DRXsleep, Aggregation state—where in Relay UE 1300 only receives data anddoes not transmit. Therefore it accumulates and aggregates the datapertaining to one or more remote UEs 1314 a, 1314 b, 1314 c,Sidlelink_TX state—wherein Relay UE 1300 undertakes only transmission onside-link but does not receive data. Therefore, the Relay UE 1300 cantransmit the data aggregated previously in aggregation state in burstmode, and Relaying state—wherein Relay UE 1300 undertakes simultaneousreception and transmission of the data on the main link (cellular link)and side-link. Therefore, aggregation factor is defined for a givenservice and is dependent on service QoS bound, average sleep delay forRelay, and further constrained by DRX alignment to assign optimum DRXcycle length and to select those Rx opportunities meeting awake periodof DRX cycle. DRX alignment also considers the DRX pattern, remote UEmay be already subjected to under its own network. Therefore,aggregation factor determines how much data aggregation is carried outat Relay UE before transmitting packet towards Remote UE.

According to another embodiment of the present invention, both Mode 1and Mode 2 resource scheduling need to be governed by the relevantservice QCI requirement for the Remote UE e.g. for VOIP/emergency calls.In view of the present invention, when Remote UE is not in RRC connectedstate, the Relay UE takes up the scheduling of the resources based onthe service QoS requirements e.g. semi-persistent or dynamic schedulingbased on service nature.

According to an embodiment of the present invention, the QoSsatisfaction is tightly intermingled with DRX operation and though they,in general, seem inversely related i.e. better DRX/EE leads to poor QoSor vice versa; The embodiments of the present invention discloses amethod to jointly optimize both these parameters. It determines thefollowing conditions for scheduling decisions in a DRX situation:

-   -   Remaining active time after which remote UE would undergo for        DRX    -   When remote UE is already in DRX, how much DRX time remaining        before waking up again and having scheduled transmission        opportunity

Accordingly, new parameters which consider the prioritization ofscheduling for remote UE which is about to go for DRX and DRX state ofconcerned remote UE when service data emerges for transmission towardsit. This enables ensuring quick delivery and avoiding packet loss.

According to another embodiment of the present invention, the processcomprises of raising the priority of the service for remote UE which isjust about to go to DRX instead of applying a continuous function ofremaining active time unlike as discussed earlier. That is, at the lastscheduling event post which a particular remote UE would go to DRX, itsDRX sleep period is added to its delay while evaluating the schedulingdecision. Effectively, considered delay is obtained by adding the DRXdelay to the queued packet delay at the immediate last scheduling eventbefore a particular remote UE goes into DRX.

Since relay is intermediate transmitter, invention further proposes tohave discard functionality at relay where it determines the potentialdelay and discards packet when it is not feasible to satisfy packetdelay budget, saving on the wastage of transmission resources.

The present embodiments have been described with reference to specificexample embodiments; it will be evident that various modifications andchanges may be made to these embodiments without departing from thebroader spirit and scope of the various embodiments. Furthermore, thevarious devices, modules, and the like described herein may be enabledand operated using hardware circuitry, for example, complementary metaloxide semiconductor based logic circuitry, firmware, software and/or anycombination of hardware, firmware, and/or software embodied in a machinereadable medium. For example, the various electrical structure andmethods may be embodied using transistors, logic gates, and electricalcircuits, such as application specific integrated circuit.

Although the embodiments herein are described with various specificembodiments, it will be obvious for a person skilled in the art topractice the invention with modifications. However, all suchmodifications are deemed to be within the scope of the claims. It isalso to be understood that the following claims are intended to coverall of the generic and specific features of the embodiments describedherein and all the statements of the scope of the embodiments which as amatter of language might be said to fall there between.

The invention claimed is:
 1. A method for discovering user equipment(UE) over a side link in device to device (D2D) communication, themethod comprising: receiving, by a relay UE, a solicitation message froma remote UE, the solicitation message comprising first informationincluding one or more of an UE identity, QoS information, a DRXconfiguration signal or a current transmission power; scheduling, by therelay UE, a transmission based on a priority order, the priority orderbeing based on the first information; and transmitting, by the relay UE,a device discovery response with a support status message to the remoteUE based on the UE identity.
 2. The method of claim 1, wherein thetransmitting transmits the device discovery response based on at leastone of: latency bounds corresponding to the QoS information beingsupportable; energy consumption being within a threshold; a number ofcurrently served remote UEs being under a limit; a device type of theremote UE; or a bandwidth.
 3. The method of claim 1, further comprising:determining, by the relay UE, whether a relay load status is overloadedor congested, the remote UE being in a coverage area of the relay UE. 4.The method of claim 3, further comprising: transmitting, by the relayUE, a solicitation response message with an overload indication based onthe relay load status being overloaded.
 5. The method of claim 4,wherein the support status message indicates as negative based on a QoScorresponding to the QoS information not being supported by the relayUE.
 6. The method of claim 1, further comprising: checking, by the relayUE, the QoS information.
 7. The method of claim 6, wherein thescheduling schedules one or more transmissions in the priority orderbased on latency information of the remote UE.
 8. The method of claim 7,further comprising: preparing RX scheduling patterns based on thelatency information.
 9. The method of claim 8, further comprising:assigning the RX scheduling patterns to the remote UE including aligningDRXs between the relay UE and the remote UE.
 10. A relay user equipment(UE) for side-link communication comprising: at least one communicationcircuit, and at least one processor, wherein the at least one processoris configured to: receive a solicitation message from a remote UE, thesolicitation message comprising first information including one or moreof an UE identity, QoS information, a DRX configuration signal or acurrent transmission power; schedule a transmission based on a priorityorder, the priority order being based on the first information; andtransmit, via the at least one communication circuit, a device discoveryresponse with a support status message to the remote UE based on the UEidentity.
 11. The relay UE of claim 10, wherein the at least oneprocessor is configured to determine whether a relay load status isoverloaded or congested, the remote UE being in a coverage area of therelay UE.
 12. The relay UE of claim 11, wherein the at least oneprocessor is configured to transmit a solicitation response message withan overload indication based on the relay load status being overloaded.13. The relay UE of claim 12, wherein the support status messageindicates as negative based on a QoS corresponding to the QoSinformation not being supported by the relay UE.
 14. The relay UE ofclaim 10, wherein the at least one processor is configured to check theQoS information.
 15. The relay UE of claim 14, wherein the at least oneprocessor is configured to schedule one or more transmissions in thepriority order based on latency information of the remote UE.
 16. Therelay UE of claim 15, wherein the at least one processor is configuredto prepare RX scheduling patterns based on the latency information. 17.The relay UE of claim 16, wherein the at least one processor isconfigured to assign the RX scheduling patterns to the remote UEincluding aligning DRXs between the relay UE and the remote UE.
 18. Therelay UE of claim 16, wherein the at least one processor is configuredto transmit the device discovery response based on at least one of:latency bounds corresponding to the QoS information being supportable;energy consumption being within a threshold; a number of currentlyserved remote UEs being under a limit; a device type of the remote UE;or a bandwidth.
 19. A method for enabling side link relay discovery indevice to device (D2D) communication, the method comprising: receiving,by one or more relay user equipment's (UEs), a solicitation messagetransmitted by a remote UE; scheduling, by a first relay UE among theone or more relay UEs, a transmission based on a priority order; andtransmitting, by each respective relay UE among the one or more relayUEs, a solicitation response message to the remote UE, the solicitationresponse message comprising an overload status indicating whether therespective relay UE is overloaded.
 20. The method of claim 19, furthercomprising: transmitting, by each respective relay UE among the one ormore relay UEs, an overload indicator during a master information block(MIB) broadcast indicating whether the respective UE relay isoverloaded.